The present Program Project is centered on the study of the effects of cocaine and amphetamine on the signal transduction pathways of medium spiny neurons in the nucleus accumbens and neostriatum. A groups of experts in various disciplines of biomedical research proposes to carry out these studies by employing a variety of distinct but complementary approaches. Project 1 will examine the effects of acute and chronic administration of cocaine and amphetamine on the state of phosphorylation of target proteins such as phosphatase inhibitors and other intermediary transduction proteins, ion pumps, ion channels and neurotransmitter receptors. These experiments will be carried out both in vitro and in vivo using rats. Project 2 will study the possible involvement of protein phosphatase inhibitors (i.e.DARPP-32 and inhibitor-1) in the biochemical, behavioral and neurodegenerative effects of cocaine and amphetamine. This project is based on the use of mice in which the genes coding for DARPP-32 and/or inhibitor-1 have been inactivated by homologous recombination. Project 3 will be centered on the study of two other DARPP's (e.g. DARPP-16 and 21). The abundance of these phosphoproteins in nucleus accumbens and neostriatum, in particular the enrichment of DARPP-21 in the limbic striatum, and the fact that they are functionally distinct from DARPP-32 suggest that each may mediate certain of the effects of cocaine and amphetamine. The function of DARPP-16 and 21 will be investigated both by utilizing gene knock out techniques and by identifying their target proteins. Finally, the Core section will establish a general method for tissue- specific inducible knock out of selected genes, including those coding for DARPP-32, 21 and 16, and inhibitor-1. The Core will provide maintenance for all colonies of transgenic and knock out mice and will produce and maintain primary cell cultures from rat brain. A supply of key reagents, such as enzymes and antibodies (including phosphorylation state-specific antibodies), will be provided by the Core.